Update a Debian Installation ISO

To use the file preseed method, the preseed file has to be incorporated into the ISO image. This docker images can be run as a command line tool to unpack a Debian Installation ISO, for example, the netinst.iso, add files to it, and then pack it up as a fresh, bootable ISO again.

Building the Docker Image

To build the image, run this command:

docker build -t debian-update-preseed-iso:latest .

Updating A Debian Installer ISO

1. Download the ISO, for example https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.6.0-amd64-netinst.iso.

2. Create a suitable preseed.cfg, by following the instructions from the Debian preseed documemtation.

3. Run this command to add your preseed.cfg to a new image:

docker run -it --rm -v "$PWD":/work debian-update-preseed-iso:latest debian-9.6.0-amd64-netinst.iso

This will generate preseed-debian-9.6.0-amd64-netinst.iso.

1. Make the ISO availabe to the machine you want to install: burn a disk, copy the image to a USB stick, etc.

Customizing The Install

The update command will add preseed.cfg from the main directory, and all files in the initrd directory to the initrd image.

As an example, there are three scripts in the initrd/custom directory that are called from preseed.cfg at various points during the installation. This allows you to fully customize the install.

When adding files to initrd, make sure you pick names that do not conflict with regular initrd image contents.